Product Description
Concentrated cobalt octoate in mineral spirits.
Acts as a drier for oil colours and mediums.
Cobalt driers made from cobalt octoate or cobalt naphthenate are the only recommended siccatives for artists oil colours and mediums as their addition in the correct proportion has a minimal effect regarding darkening and embrittlement of the paint film.
Product Code: 011
Constituents
Cobalt Octoate, White Spirit.
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Safety Data Sheet
Product Application
Cobalt Driers may be added to oil and alkyd colours, oil mediums and drying oils in recommended measured quantities.
Cobalt Driers are known as ‘surface’ siccatives (driers) and will only speed the drying of the surface of the paint film. They are not ‘through-film’ siccatives and do not perform as successfully with thick films of oil (i.e. impasto technique)
Langridge recommends that Cobalt Driers should be added to an oil medium or artists’ drying oil rather than mixed directly into the oil paint. Measuring quantities of driers directly into small amounts of colour is difficult and prone to miscalculation.
Langridge recommends addition to mediums and oils to reduce the likelihood of over use and to simplify the artists’ studio practice. Once mixed with an oil or medium, the artist can dispense with concerns about constant ongoing additions of driers.
Add Cobalt Driers as an approximate 1% addition. (i.e. To 500ml of Linseed Oil add 5ml of Cobalt Drier.) Shake or stir well together. When initially mixed together, the driers will impart a blue/green cast to the oil or medium with which it is mixed. Exposed to indirect sunlight for a few days will remove this colour difference (Exposing the oil or medium to indirect sunlight will not sun bleach or thicken the material). If used in correct proportions, the colour of the cobalt drier will not interfere with oil paint brightness or colour saturation.
Driers made from lead, manganese and other proprietorial mixtures that do not wholly contain cobalt driers are to be avoided as they promote darkening and loss of flexibility. However, even Langridge Cobalt Driers are to be used sparingly as its over-use will destroy paint films.
Additional Product Information
General guide to drying rates using Langridge Cobalt Driers:
No addition 1% addition
Linseed Oil 2-3 days 1 day
Poppy/Safflower Oil 7 days 4 days
Stand Oil (100%) 14 days 7 days
Stand Oil + Gum Turpentine (1:1) 7 days 4 days
Lean Medium (1 part Linseed Oil + 3 parts Gum Turpentine) 2 days 1 day
General Medium (1 part Linseed Oil + 1 part Gum Turpentine) 2 days 1 day
The table provides drying times based on a 10 micron thickness film of oil/medium applied as a drawdown over a non-absorbent card. Times listed are for paint films reaching a non-tack surface and not for complete through-film drying. Due to the variable nature of the artists painting technique, drying times may vary for complete drying.
Problems with ambient temperature and humidity
Because artists drying oils (oils that dry to a hard, non-reversible film) absorb oxygen to harden, so the ambient temperature and humidity have an effect on the speed and success of film hardening. Oils, oil paints and oil mediums should not be applied in temperatures below 10ºC (50ºF) or above 40ºC (104ºF). The relative humidity level should not exceed 50%. Moisture in a high humidity environment will create a fine layer of water on top of the paint film preventing oxygen from being absorbed. This will dramatically slow the hardening of the oil, potentially weakening the paint film even when fully dry. Temperature and relative humidity can be controlled in the artists studio with heating/cooling devices and the use of dehumidifying devices.
Accelerating the drying rate of a completed painting
Cobalt Driers should not be applied to a painting to accelerate the drying of an already laid paint film. If a painting is taking longer to dry than is expected, it is recommended to place the artwork in a dry, warm, dust-free area with a steady airflow across the surface. Once paint has been applied to a painting no attempt should be made to add driers or rapid drying mediums on top to accelerate drying. This can lead to cracking and potential flaking of the paint film.
Accelerating the drying rate of varnishes
Cobalt Driers cannot speed the drying of artists’ varnishes as they contain no oil. Artists’ varnishes dry by evaporation of the solvent. If a varnish remains tacky for longer than is recommended by the manufacturer, this may be due to latent solvent trapped in the preceding paint film. As it attempts to evaporate through the surface it will dissolve the resin of the varnish. Place the artwork in a dry, warm, dust-free area with a steady airflow across the surface.
Working Properties
Thinning
For best results thin with Artists’ White Spirit. However, Langridge Low Toxic Solvent may be substituted.
Appearance
Langridge Cobalt Driers is a dark blue colour liquid with a characteristic White Spirit odour.
Clean Up
Clean measuring containers with Artists’ White Spirit. Langridge Low Toxic Solvent may be substituted. For further washing apply a small quantity of Langridge Safe-Clean-Up or Marseille or other pure olive oil soap to release any remaining colour. Wash thoroughly in warm water. Leave brushes to fully dry before using for oil colours.
Available in:
100ml (0111), 500ml (0115), Litre (011L), 4 Litre (0114), 20 Litre (0112)